The present invention relates to an ultraviolet blocking material, and more particularly to a breathable ultraviolet blocking material.
Ultraviolet radiation is to be credited with certain therapeutic applications--for example, the treatment of psoriasis--but is far better known for its harmful effect on skin ranging from the simple sunburn to a dried-out, prematurely wrinkled skin, cataracts, and skin cancer. While the present application is concerned particularly with the protection of human beings from the delterious effects of ultraviolet radiation, such effects extend beyond humans and encompass other animals, food stuffs, medicines, upholstery and the like.
Ultraviolet radiation refers to that portion of the spectrum just beyond the violet on the short-wavelength side, generally 200-400 nm. At least with respect to human skin, the most pertinent portions of the spectrum are considered to be UVA radiation (about 320-400 nm) and UVB radiation (about 290-320 nm). Topical sunscreens contain absorber chemicals which can be applied directly to the skin to block transmission of at least some UV radiation, for example, by absorbing it. The topical sunscreens have not proven to be entirely satisfactory in use, however. They are typically inconvenient to apply, expensive, require frequent re-application, may cause photosensitivity reactions, allergic contact dermatitis or acne cosmetica, may stain clothing yellow and provide only a relatively low level of UVA protection.
Untreated yarn may itself block the transmission of ultraviolet radiation and, if it does not, can frequently be treated to provide such a function. Thus, tightly knit or double knit clothing may be used to protect against ultraviolet radiation, but such clothing is clearly uncomfortable to wear in warm weather, precisely when the need for sun protection is greatest. Indeed, UV blockers have been incorporated into textile fibers (such as wool) to protect them from the deleterious effects thereon of ultraviolet radiation. In such instances, however, it is the fibers of the fabric--or the added UV blocker deposited on the fibers--which provide protection against UV transmission and thus a dense material, such as a double knit, closely woven, or woven of densely intermeshed fibers, must be employed. For example, if the fibers of the fabric are only loosely intermeshed or if the interstices defined by the threads of a woven fabric are large, ultraviolet radiation which might otherwise be stopped by the fibers can pass through the apertures to reach the wearer unless the fabric is layered. See Acta. Derm. Venereol. (1980), Vol. 60, pp. 459-460, B. Berne et al., "Protective Effects of Various Types of Clothes Against UV Radiation"; Clin. Exp. Dermatol. (1981) Vol. 6, pp. 577-582, esp. p. 581, C. Welsh et al., "The Protection Against Solar Actinic Radiation Afforded By Common Clothing Fabrics"; Arch. Dermotol. (1985), Vol. 121, pp. 1400-1402; Dermotologic Clinics (1986), Vol. 4, No. 2, pp. 321-334, esp. p. 331, M. Pathak, "Sunscreens"; Japanese Patent No. 59,179,878 (underwear fabric containing UV absorber). Such a dense material or layered clothing makes the wearer warm and is thus not acceptable for wear at the beach and other places most requiring UV sunscreen protection. Thus, the need remains for a material which combines the ability to afford the wearer a high degree of ultraviolet radiation protection with breathability (that is, moisture vapor permeability) and porosity.
Accordingly, it is an object of the present invention to provide an ultraviolet blocking material which is based on a breathable fabric of loosely intermeshed fibers.
Another object is to provide such a material which is based on a breathable fabric defining porosity-creating apertures and yet provides ultraviolet blocking even in the apertures.
A further object is to provide such a material which, if desired, is breathable.
It is also an object to provide such a material which is lightweight, inexpensive, comfortable to wear and easy to maintain.